Skeletal structure of dicephalic twins. B. C. Hirst & G. A. Piersol, Human monstrosities. Wellcome L0027955. (1893)
Dicephalic parapagus () is a rare form of
partial twinning with two heads side by side on one
torso
The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a huma ...
.
Infants conjoined this way are sometimes called "two-headed babies" in popular media. The condition is also called parapagus dicephalus.
If carried to term, most dicephalic twins are
stillborn
Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The ter ...
, or die soon after birth.
A small number are known to have survived to adulthood.
The extent to which limbs and organs are duplicated varies from case to case. One head may be only partially developed (
anencephalic), or both may be complete. In some cases, two complete hearts are present as well, which improves their chances of survival. The total number of arms may be two, three or four.
Their prospects are best if no attempt is made to separate them, except in cases in which one twin is clearly dying.
Terminology
Dicephalus means two-headed.
Parapagus means joined side by side.
Dicephalic twins are called:
* dibrachius if they have two arms altogether (one for each twin),
* tribrachius, if they have three arms altogether,
* tetrabrachius, if they have four arms altogether,
* dipus, if they have two legs altogether (one for each twin).
Incidence
Conjoined twins appear in one in 50,000 to one in 100,000 births.
Dicephalic twins represent about 11 percent of all conjoined twins.
Medical and social response
As late as the 1960s, some medical publications argued that newborn dicephalic twins should not be actively treated or resuscitated. An attempt at surgical separation was reported in a paper published in 1982, but did not result in long-term survival of either twin. In more recent cases in Turkey and Minnesota, doctors advised that separation surgery would not be appropriate.
Dicephalic twins who survived past infancy
Giacomo and Giovanni Battista Tocci (1877–1940), were Italian male dicephalus parapagus twins who survived to adulthood.
Each had his own pair of arms.
They had two legs all together, one of which was controlled by each twin. They were exhibited in
freak show
A freak show, also known as a creep show, is an exhibition of biological rarities, referred to in popular culture as "freaks of nature". Typical features would be physically unusual humans, such as those uncommonly large or small, those with ...
s as children and teenagers. The Toccis learned to speak several languages, but never learned to walk.
, born in Minnesota in 1990, also are dicephalus parapagus twins. They were born with two functional arms, plus a vestigial third arm, which was surgically removed.
Each twin has her own complete head, heart and spine, and controls one arm and one leg.
They learned to walk around the same age as average children, went on to attend school, learn to drive, play sports,
and completed courses at college.
Twin girls were born in Turkey in 2000.
They were conjoined like the Tocci brothers, with four arms and two legs all together. As with the Toccis and the Hensels, it was found that each twin controlled one leg.
Because of the size of their upper body, the Turkish twins needed a special program of exercises before they could learn to walk.
After that, they learned to run and climb stairs without further specialist help, and at age 11 they were going to school with other children.
See also
*
Craniopagus parasiticus is another form of partial twinning which results in two heads kept alive by a single torso. In these cases a second, vestigial torso is present, and the heads are joined directly to one another.
*
Diprosopus
Diprosopus ( el, διπρόσωπος, "two-faced", from , , "two" and , euter "face", "person"; with Latin ending), also known as craniofacial duplication (cranio- from Greek , "skull", the other parts Latin), is an extremely rare congenital di ...
is a condition in which there are duplicated facial features on one head.
*
Polycephaly is a general term about organisms with more than one head.
References
{{Reflist
Conjoined twins
